<!DOCTYPE html>
<!--<div class="menu__subheader"><br>微信公众号：雁卿雁卿呀-->
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>线条绘制爱心表白</title>
	<meta name="author" content="Logical Digit">
  </head>
      <!-- css部分 -->
 <style>
  body {
    background-color: #000;
    margin: 0;
    overflow: hidden;
    background-repeat: no-repeat;
}
 </style>
  <body>
  <div style="zoom: 150%">
<a href="https://mp.weixin.qq.com/s/2EnWoe1bOKAOFh2QyPkeZg" class="hide_buttom"
  style="position: fixed;top: 10%;right: 10px;width: 35px;height: 35px;z-index: 19999;background: #696969;border-radius: 50%;padding: 1.0px;text-align: center;color: #ddd;text-decoration: none;   clear: both; line-height: 35px; 	margin:auto;   font-size: 13px;">制作</a>
<a href="https://mp.weixin.qq.com/s/KA3nFLUB5W8f1BIyd_g0cg" class="hide_buttom"
  style="position: fixed;top: 4%;right: 10px;width: 35px;height: 35px;z-index: 19999;background: #696969;border-radius: 50%;padding: 1.0px;text-align: center;color: #ddd;text-decoration: none;   clear: both; line-height: 35px; 	margin:auto;   font-size: 13px;   ">更多</a>
</div>
    <!-- 绘画爱心 -->
    <canvas id="canvas" width="1400" height="600"></canvas>
    <!-- js部分 -->
  </body>
  <script>
var canvas = document.getElementById("canvas");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
// Initialize the GL context
var gl = canvas.getContext('webgl');
if (!gl) {
    console.error("Unable to initialize WebGL.");
}
//Time step
var dt = 0.015;
//Time
var time = 0.0;
//************** Shader sources **************
var vertexSource = `
attribute vec2 position;
void main() {
	gl_Position = vec4(position, 0.0, 1.0);
}
`;
 
var fragmentSource = `
precision highp float;
uniform float width;
uniform float height;
vec2 resolution = vec2(width, height);
uniform float time;
#define POINT_COUNT 8
vec2 points[POINT_COUNT];
const float speed = -0.5;
const float len = 0.25;
float intensity = 0.9;
float radius = 0.015;
//https://www.shadertoy.com/view/MlKcDD
//Signed distance to a quadratic bezier
float sdBezier(vec2 pos, vec2 A, vec2 B, vec2 C){    
	vec2 a = B - A;
	vec2 b = A - 2.0*B + C;
	vec2 c = a * 2.0;
	vec2 d = A - pos;
	float kk = 1.0 / dot(b,b);
	float kx = kk * dot(a,b);
	float ky = kk * (2.0*dot(a,a)+dot(d,b)) / 3.0;
	float kz = kk * dot(d,a);      
	float res = 0.0;
	float p = ky - kx*kx;
	float p3 = p*p*p;
	float q = kx*(2.0*kx*kx - 3.0*ky) + kz;
	float h = q*q + 4.0*p3;
	if(h >= 0.0){ 
		h = sqrt(h);
		vec2 x = (vec2(h, -h) - q) / 2.0;
		vec2 uv = sign(x)*pow(abs(x), vec2(1.0/3.0));
		float t = uv.x + uv.y - kx;
		t = clamp( t, 0.0, 1.0 );
		// 1 root
		vec2 qos = d + (c + b*t)*t;
		res = length(qos);
	}else{
		float z = sqrt(-p);
		float v = acos( q/(p*z*2.0) ) / 3.0;
		float m = cos(v);
		float n = sin(v)*1.732050808;
		vec3 t = vec3(m + m, -n - m, n - m) * z - kx;
		t = clamp( t, 0.0, 1.0 );
		// 3 roots
		vec2 qos = d + (c + b*t.x)*t.x;
		float dis = dot(qos,qos);
        
		res = dis;
		qos = d + (c + b*t.y)*t.y;
		dis = dot(qos,qos);
		res = min(res,dis);
		
		qos = d + (c + b*t.z)*t.z;
		dis = dot(qos,qos);
		res = min(res,dis);
		res = sqrt( res );
	}
    
	return res;
}
//http://mathworld.wolfram.com/HeartCurve.html
vec2 getHeartPosition(float t){
	return vec2(16.0 * sin(t) * sin(t) * sin(t),
							-(13.0 * cos(t) - 5.0 * cos(2.0*t)
							- 2.0 * cos(3.0*t) - cos(4.0*t)));
}
//https://www.shadertoy.com/view/3s3GDn
float getGlow(float dist, float radius, float intensity){
	return pow(radius/dist, intensity);
}
float getSegment(float t, vec2 pos, float offset, float scale){
	for(int i = 0; i < POINT_COUNT; i++){
		points[i] = getHeartPosition(offset + float(i)*len + fract(speed * t) * 6.28);
	}
    
	vec2 c = (points[0] + points[1]) / 2.0;
	vec2 c_prev;
	float dist = 10000.0;
    
	for(int i = 0; i < POINT_COUNT-1; i++){
		//https://tinyurl.com/y2htbwkm
		c_prev = c;
		c = (points[i] + points[i+1]) / 2.0;
		dist = min(dist, sdBezier(pos, scale * c_prev, scale * points[i], scale * c));
	}
	return max(0.0, dist);
}
void main(){
	vec2 uv = gl_FragCoord.xy/resolution.xy;
	float widthHeightRatio = resolution.x/resolution.y;
	vec2 centre = vec2(0.5, 0.5);
	vec2 pos = centre - uv;
	pos.y /= widthHeightRatio;
	//Shift upwards to centre heart
	pos.y += 0.02;
	float scale = 0.000015 * height;
	
	float t = time;
    
	//Get first segment
	float dist = getSegment(t, pos, 0.0, scale);
	float glow = getGlow(dist, radius, intensity);
    
	vec3 col = vec3(0.0);
    
	//White core
	col += 10.0*vec3(smoothstep(0.003, 0.001, dist));
	//Pink glow
	col += glow * vec3(0.94,0.14,0.4);
    
	//Get second segment
	dist = getSegment(t, pos, 3.4, scale);
	glow = getGlow(dist, radius, intensity);
    
	//White core
	col += 10.0*vec3(smoothstep(0.003, 0.001, dist));
	//Blue glow
	col += glow * vec3(0.2,0.6,1.0);
        
	//Tone mapping
	col = 1.0 - exp(-col);
	//Output to screen
 	gl_FragColor = vec4(col,1.0);
}
`;
 
//************** Utility functions **************
 
window.addEventListener('resize', onWindowResize, false);
 
function onWindowResize() {
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
    gl.viewport(0, 0, canvas.width, canvas.height);
    gl.uniform1f(widthHandle, window.innerWidth);
    gl.uniform1f(heightHandle, window.innerHeight);
}
 
 
//Compile shader and combine with source
function compileShader(shaderSource, shaderType) {
    var shader = gl.createShader(shaderType);
    gl.shaderSource(shader, shaderSource);
    gl.compileShader(shader);
    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
        throw "Shader compile failed with: " + gl.getShaderInfoLog(shader);
    }
    return shader;
}
 
//From https://codepen.io/jlfwong/pen/GqmroZ
//Utility to complain loudly if we fail to find the attribute/uniform
function getAttribLocation(program, name) {
    var attributeLocation = gl.getAttribLocation(program, name);
    if (attributeLocation === -1) {
        throw 'Cannot find attribute ' + name + '.';
    }
    return attributeLocation;
}
 
function getUniformLocation(program, name) {
    var attributeLocation = gl.getUniformLocation(program, name);
    if (attributeLocation === -1) {
        throw 'Cannot find uniform ' + name + '.';
    }
    return attributeLocation;
}
 
//************** Create shaders **************
 
//Create vertex and fragment shaders
var vertexShader = compileShader(vertexSource, gl.VERTEX_SHADER);
var fragmentShader = compileShader(fragmentSource, gl.FRAGMENT_SHADER);
 
//Create shader programs
var program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
 
gl.useProgram(program);
 
//Set up rectangle covering entire canvas 
var vertexData = new Float32Array([-1.0, 1.0, // top left
    -1.0, -1.0, // bottom left
    1.0, 1.0, // top right
    1.0, -1.0, // bottom right
]);
 
//Create vertex buffer
var vertexDataBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertexDataBuffer);
gl.bufferData(gl.ARRAY_BUFFER, vertexData, gl.STATIC_DRAW);
 
// Layout of our data in the vertex buffer
var positionHandle = getAttribLocation(program, 'position');
 
gl.enableVertexAttribArray(positionHandle);
gl.vertexAttribPointer(positionHandle,
    2, // position is a vec2 (2 values per component)
    gl.FLOAT, // each component is a float
    false, // don't normalize values
    2 * 4, // two 4 byte float components per vertex (32 bit float is 4 bytes)
    0 // how many bytes inside the buffer to start from
);
 
//Set uniform handle
var timeHandle = getUniformLocation(program, 'time');
var widthHandle = getUniformLocation(program, 'width');
var heightHandle = getUniformLocation(program, 'height');
 
gl.uniform1f(widthHandle, window.innerWidth);
gl.uniform1f(heightHandle, window.innerHeight);
 
function draw() {
    //Update time
    time += dt;
 
    //Send uniforms to program
    gl.uniform1f(timeHandle, time);
    //Draw a triangle strip connecting vertices 0-4
    gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
 
    requestAnimationFrame(draw);
}
 
draw();
  </script>
</html>